Acid-degradable resin compositions containing ketene-aldehyde copolymer

ABSTRACT

It is intended to provide compositions to be used in resists and the like for forming fine patterns with a high sensitivity and a high resolution by increasing the difference in the solubilities between exposed parts and unexposed parts. Acid-degradable compositions contain a polymer having a repeating unit represented by the following general formula (I):  
                 
 
wherein R 1  and R 2  independently represent hydrogen atom, halogen atom, C 1-20  hydrocarbon group, a heterocyclic group, a cyano group, a nitro group, C(═O)R 4  group, S(O) n R 4  group, P(═O)(R 4 ) 2  group or M(R 4 ) 3  group; R 3  represents C 1-20  hydrocarbon group or a heterocyclic group: R 4  represents C 1-20  hydrocarbonoxy group, C 1-20  hydrocarbon group, C 1-20  hydrocarbonthio group or mono- or di-C 1-20  hydrocarbonamino group; M represents a silicon, germanium, tin or lead atom; and n is  0, 1  or  2 , and an acid or a compound capable of generating an acid in response to an external stimulus.

TECHNICAL FIELD

The present invention relates to a resist composition used forproduction of a semiconductor element and so forth. In particular, thepresent invention relates to a resist composition which is useful forforming a positive pattern using far ultraviolet rays of 300 nm or less,such as KrF excimer laser, or electron beam as exposure energy. Thepresent invention also relates to a resin composition having stabilityto some extent yet main chains thereof may be cut by an acid to bedissociated into molecules of low molecular weight so as to be easilyremoved.

BACKGROUND ART

A chemical amplification type resist including an alkali soluble resin,an acid generator, and a solubility controlling agent having an acidunstable group is conventionally known as a resist composition used forproduction of a semiconductor element and so forth. In this type ofcomposition, acid is generated from the acid forming agent whenirradiated by ultraviolet rays, electron beam, or X-ray, and the acidthus generated makes chain reaction with the acid unstable groups tochange the solubility of the alkali soluble resin so as to form apattern. As the alkali soluble resin, a novolak resin, a phenol resin,an acryl resin, or copolymers thereof may be used, and there are casesin which an alkali soluble resin also serves as a solubility controllingagent having an acid unstable group, or a resin having an acid unstablegroup reacts with an acid to become alkali soluble.

However, since the difference in solubility in exposed parts andunexposed parts is generated by the presence or absence of acid unstablegroups in a conventional chemical amplification type resist, it isconsidered that there is a limitation of some degree in performing afine process.

An object of the present invention includes to provide a highsensitivity and high resolution resist composition which may be used forforming fine patterns by increasing the difference in solubility betweenexposed parts and unexposed parts.

DISCLOSURE OF INVENTION

Inventors of the present invention, after making diligent studies tosolve the above problem, found that a resist composition includingpolymers of particular combination having an ester bonding in its mainchain as a polymer component can achieve the above object, and completedthe present invention.

That is, the present invention relates to:

-   (1) an acid degradable composition including a polymer having a    repeating unit represented by the following general formula (I):    wherein R₁ and R₂ independently represent hydrogen atom, halogen    atom, C₁₋₂₀ hydrocarbon group, a heterocyclic group, a cyano group,    a nitro group, C(═O)R₄ group, S(O)_(n)R₄ group, P(═O)(R₄)₂ group or    M(R₄)₃ group; R₃ represents C₁₋₂₀ hydrocarbon group or a    heterocyclic group; R₄ represents C₁₋₂₀ hydrocarbonoxy group, C₁₋₂₀    hydrocarbon group, C₁₋₂₀ hydrocarbonthio group or mono- or di-C₁₋₂₀    hydrocarbonamino group; M represents a silicon, germanium, tin or    lead atom; and n is 0, 1 or 2, and an acid or a compound capable of    generating an acid in response to an external stimulus;-   (2) an acid-degradable composition as set forth in (1), wherein the    external stimulation is at least one selected from the group    consisting of heat, pressure, and radiation, and-   (3) an acid-degradable composition as set forth in (1), wherein the    compound capable of generating an acid in response to an external    stimulus is a photosensitive compound which generates an acid by    radiation irradiation.

The present invention also relates to:

-   (4) a photoresist composition, including: a polymer component having    a repeating unit represented by the following general formula (I):    wherein R₁ and R₂ independently represent hydrogen atom, halogen    atom, C₁₋₂₀ hydrocarbon group, a heterocyclic group, a cyano group,    a nitro group, a C(═O)R₄ group, S(O)_(n)R₄ group, P(═O)(R₄)₂ group    or M(R₄)₃ group; R₃ represents C₁₋₂₀ hydrocarbon group or a    heterocyclic group: R₄ represents C₁₋₂₀ hydrocarbonoxy group, C₁₋₂₀    hydrocarbon group, C₁₋₂₀ hydrocarbonthio group or mono- or di-C₁₋₂₀    hydrocarbonamino group; and M represents a silicon, germanium, tin    or lead atom;-   (5) a photoresist composition, including the acid-degradable    composition as set forth in any one of (1)-(3);-   (6) a photoresist composition as set forth in (4) or (5), further    including solvent;-   (7) a photoresist composition as set forth in any one of (4)-(6),    further including a basic compound;-   (8) a composition as set forth in any one of (1)-(7), wherein the R₁    and R₂ independently represent C₁₋₂₀ hydrocarbon group, and the R₃    represents C₁₋₂₀ hydrocarbon group or a heterocyclic group in the    general formula (I);-   (9) a composition as set forth in any one of (1)-(8), wherein the R₃    in the formula (I) is a substituent represented by the following    formula (II):    wherein R₅ represents hydrogen, or an acid degradable.eliminable    group, R₆ represents a halogen atom or C₁₋₂₀ hydrocarbon group, m    represents an integer of 1-3 and p represents 0 or an integer of 1-3    so as to satisfy m+p≦5, and when m is 2 or greater, R₅ may be the    same or different from each other, and when p is 2 or greater, R₆    may be the same or different from each other;-   (10) a composition as set forth in any one of (1)-(9), wherein a    number average molecular weight of the polymer having the repeating    unit represented by the formula (I) is within a range of 2,000 to    50,000, and-   (11) a composition as set forth in any one of (1)-(10), wherein a    ratio (Mw/Mn) of a weight average molecular weight (Mw) and a number    average molecular weight (Mn) of the polymer having the repeating    unit represented by the formula (I) is within a range of 1.01 to    3.00.

In the repeating units represented by the formula (I) used in thepresent invention, R₁ and R₂ independently represent hydrogen, halogenatom, C₁₋₂₀ hydrocarbon group, a heterocyclic group, a cyano group, anitro group, C(═O)R₄ group, S(O)_(n)R₄ group, P(═O)(R₄)₂ group or M(R₄)₃group; R₃ represents C₁₋₂₀ hydrocarbon group or a heterocyclic group: R₄represents C₁₋₂₀ hydrocarbonoxy group, C₁₋₂₀ hydrocarbon group, C₁₋₂₀hydrocarbonthio group or mono- or di-C₁₋₂₀ hydrocarbonamino group; Mrepresents a silicon, germanium, tin or lead atom; and n is 0, 1 or 2.Specific examples of R₁ and R₂ include hydrogen atom, halogen atoms,such as fluorine atom, chlorine atom, and bromine atom, C₁₋₂₀ alkylgroups, such as methyl group, ethyl group, n-propyl group, isopropylgroup, n-butyl group, t-butyl group, s-butyl group, isobutyl group,n-pentyl group, s-pentyl group, isopentyl group, neopentyl group,n-hexyl group, s-hexyl group, 1,1-dimethyl-n-hexyl group, n-heptylgroup, n-decyl group, and n-dodecyl group, C₂₋₂₀ alkynyl groups, such asvinyl group, allyl group, 2-butenyl group, 1-methyl-2-propenyl group,and 4-octenyl group, C₂₋₂₀ alkynyl groups, such as ethynyl group,propargyl group, and 1-methyl-propynyl group, C₃₋₂₀ alicyclichydrocarbon groups, such as cyclopropyl group, cyclobutyl group,cyclopentyl group, 1-methylcyclopentyl group, 1-methylcyclohexyl group,1-adamantyl group, 1-methyladamantyl group, 2-adamantyl group,2-methyl-2-adamantyl group, and norbonyl group, C₆₋₂₀ aromatichydrocarbon groups, such as phenyl group, 1-naphthyl group, and9-anthracenyl group, heterocyclic groups, such as 2-pyridyl group,3-pyridyl group, 4-pyridyl group, 2-furanyl group, 2-thienyl group,3-thienyl group, 1-pyrrolo group, 2-oxazolyl group, 3-isooxazolyl group,2-thiazolyl group, 3-isoazolyl group, 1-pyrrazolyl group, 4-pyrrazolylgroup, 2-imidazolyl group, 1,3,4-oxadiazole-2-yl, 1,2,4-oxadiazole-5-yl,1,3,4-thidiazole-2-yl, 1,2,4-thiadiazole-5-yl, 1,3,4-triazole-2-yl,1,2,3-thiadiazole-5-yl, 1,2,3-triazole-4-yl, 1,2,3,4-tetrazole-5-yl,pyrimidine-2-yl, pyrimidine-4-yl, pyrazine-2-yl, pyridazine-3-yl,1,2,4-triazine-6-yl, 1,3,5-triazine-2-yl, 1-pyrrolidinyl group,1-pyperidyl group, 4-morpholinyl group, 2-tetrahydrofuranyl group, and4-tetrahydropyranyl group, C₁₋₂₀ alkoxycarbonyl groups, such asmethoxycarbonyl group, ethoxycarbonyl group, n-propoxycarbonyl group,isopropoxycarbonyl group, n-butoxycarbonyl group, and t-butoxycarbonylgroup, C₁₋₂₀ alkylthiocarbonyl groups, such as methylthiocarbonyl group,substituted or unsubstituted carbamoyl groups, such asN,N-dimethylcarbamoyl group, substituted or unsubstituted sulfamoylgroups, such as methylsulfenyl group, phenylsulfenyl group, methylsulfinyl group, phenyl sulfinyl group, methylsulfonyl group,phenylsulfonyl group, methylsulfuryl group, and N,N-dimethylsulfamoylgroup, phosphonyl groups, such as dimethylphosphonyl group,bis-methylthiophosphonyl group, and tetramethylaminophosphonyl group,trimethylsilyl group, t-butyldimethylsilyl group, phenyldimethylsilylgroup, trimethylstannyl group, and triphenylpranbanyl group.

Also, R₃ represents C₁₋₂₀ hydrocarbon groups, and heterocyclic groups,and specific examples thereof include the same substituents explainedfor R₁ and R₂.

Each of the substituents for R₁ to R₃ described above may havesubstituents attached to suitable carbon atoms. Example of suchsubstituents include halogen atoms, such as fluorine atom, chlorineatom, and bromine atom, C₁₋₂₀ alkyl groups, such as methyl group, ethylgroup, n-propyl group, isopropyl group, n-butyl group, t-butyl group,n-hexyl group, fluoromethyl group, difluoromethyl group, trifluoromethylgroup, perfluoroethyl group, cyclopropyl group, and cyclohexyl group,vinyl group, allyl group, phenyl group, substituted phenyl groups, suchas 4-chlorophenyl group, 4-methoxyphenyl group, and 3,4-dimethylphenylgroup, hydrocarbon groups, such as propargyl group,2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl group, and2-(ethoxymethoxy)-1,1,1,3,3,3-hexafluoro-2-propyl group, alkoxy groups,such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group,n-butoxy group, s-butoxy group, isobutoxy group, t-butoxy group,fluoromethoxy group, difluoromethoxy group, trifluoromethoxy group,phenoxy group, 4-chlorophenoxy group, benzyloxy group, phenethyloxygroup, t-butoxycarbonyloxy group, tetrahydropyranyloxy group,phenoxyethoxy group, ethoxyethoxy group, trimethylsilyloxy group, andt-butoxycarbonylmethoxy group, amino groups, such as amino group,methylamino group, dimethylamino group, and t-butoxycarbonylamino group,alkyltio, arylthio, or heterocyclicthio groups or oxidants thereof, suchas methylthio group, phenylthio group, 2-pyrridylthio group,methylsulfenyl group, and methylsulfonyl group, C₁₋₂₀ alkoxycarbonylgroups, such as methoxycarbonyl group, ethoxycarbonyl group,n-propoxycarbonyl group, isopropoxycarbonyl group, n-butoxycarbonylgroup, and t-butoxycarbonyl group, C₂₋₂₀ acyl groups, such as acetylgroup, propanoyl group, benzoyl group, and 2-pyrridylcarbonyl group,cyano group, and nitro group.

Examples of R₁-R₃ group having these substituents include haloalkylgroups, such as chloromethyl group, fluoromethyl group, bromomethylgroup, dichloromethyl group, difluoromethyl group, dibromomethyl group,trichloromethyl group, trifluoromethyl group, tribromomethyl group,trichloromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethylgroup, 3,3,3-trifluoropropyl group, and 1,1,2,3,3,3-hexafluoropropylgroup, haloalkenyl groups, such as tetrafluoroethenyl group, and2,2-difluoroethenyl group, alkoxyalkyl groups, such as methoxymethylgroup, methoxyethyl group, and phenoxymethyl group, alkylthioalkylgroups or arylthioalkyl groups, such as methylthiomethyl group, andphenylthiomethyl group, aralkyl groups, such as benzyl group,diphenylmethyl group, trityl group, and phenethyl group, acylalkylgroups, such as benzoylmethyl group, and acetylmethyl group, andcyanomethyl group.

Also, preferable examples of substituents include, in particular, thoseexpressed by the formula (II). In the substituents expressed by theformula (II), R₅ represents hydrogen, or an acid removable/degradablegroup, m represents an integer of 1-3, and when m is 2 or greater, R₅may be the same or different from each other. In this specification, theterm “acid removable/degradable group” means a group which may beeliminated and/or degraded by an acid. Specific examples thereof includemethoxymethyl group, 2-methoxyethoxymethyl group,bis(2-chloroethoxy)methyl group, tetrahydropyranyl group,4-methoxytetrahydropyranyl group, tetrahydrofuranyl group,triphenylmethyl group, trimethylsilyl group,2-(trimethylsilyl)ethoxymethyl group, t-butyldimethylsilyl group,trimethylsilylmethyl group, and substituents expressed by the followingformulae:

wherein k represents 0 or 1, and further may include a group expressedby the following formula:

wherein R₁₄ represents C₁₋₂₀ unsubstituted or alkoxy substituted alkylgroup, C₅₋₁₀ cycloalkyl group, or C₆₋₂₀ unsubstituted or alkoxysubstituted aryl group, R₁₅ represents hydrogen or C₁₋₃ alkyl group, R₁₆represents hydrogen, C₁₋₆ alkyl group, or C₁₋₆ alkoxy group. Specificexamples of such substituents include 1-methoxyethyl group,1-ethoxyethyl group, 1-methoxypropyl group, 1-methyl-1-methoxyethylgroup, and 1-(isopropoxy)ethyl group. The position of substitutingalkoxy group (OR₅ group) is not particularly limited, however, meta- orpara-positions are preferable.

Also, R₆ represents a halogen atom, or C₁₋₂₀ hydrocarbon group. Specificexamples thereof include the substituents of R₁ and R₂ which correspondto the above limitations, and the substituting position thereof is notparticularly limited. Also, p represents 0 or an integer of 1-3, andsatisfies the relationship of m+p≦5. When p is 2 or greater, R₆ may bethe same or different from each other.

Specific examples of the substituents expressed by the formula (II)include 4-hydroxyphenyl group, 4-hydroxy-3-methylphenyl group,4-t-butoxyphenyl group, 4-tetrahydropyranyloxyphenyl group,4-phenoxyethoxyphenyl group, 4-trimethylsilyloxyphenyl group,4-t-butoxycarbonyloxyphenyl group, 4-t-butoxycarbonylmethoxyphenylgroup, 2,3-difluoro-4-hydroxyphenyl group, 2,3-difluoro-4-t-butoxyphenylgroup, 2,6-difluoro-4-hydroxyphenyl group, 2,6-difluoro-4-t-butoxyphenylgroup, 3,5-difluoro-4-hydroxyphenyl group, 3,5-difluoro-4-t-butoxyphenylgroup, 2,3,5,6-tetrafluoro-4-hydroxyphenyl group,2,3,5,6-tetrafluoro-4-t-butoxyphenyl group,2-trifluoromethyl-4-hydroxyphenyl group,2-trifluoromethyl-4-t-butoxyphenyl group,2-trifluoromethyl-6-fluoro-4-hydroxyphenyl group,2-trifluoromethyl-6-fluoro-4-t-butoxyphenyl group,3-trifluoromethyl-5-fluoro-4-hydroxyphenyl group,3-trifluoromethyl-5-fluoro-4-t-butoxyphenyl group,4-(1-ethoxyethoxy)phenyl group,4-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)phenyl group,4-(2-ethoxymethoxy-1,1,1,3,3,3-hexafluoro-2-propyl)phenyl group, and soforth.

The substituents expressed by the formula (II), which indicate thepreferable examples for R₃, are also preferable examples of substituentsfor R₁ and R₂.

Moreover, each of the substituents expressed as R₁-R₃ need not be thesame throughout all of the repeating units expressed by the formula (I),and two or more different kinds of substituents may be suitably used.For example, as a substituent of R₃, p-methoxyphenyl group andp-(1-ethoxyethoxy)phenyl group may be used in the form of a mixture withthe molar ratio of 1/99 to 99/1.

The polymer having the repeating unit expressed by the formula (I) ofthe present invention means polymers which include only the repeatingunit expressed by the formula (I), and polymers which include therepeating unit expressed by the formula (I) and repeating unitsexpressed by other than the formula (I).

Specific examples of the repeating units other than the repeating unitexpressed by the formula (I) include the repeating unit expressed by thefollowing formula (III):

wherein R₃₁, R₃₂, and R₃₃ independently represent hydrogen atom,fluorine atom, C₁₋₂₀ linear, branch, or cyclic alkyl group orfluorinated alkyl group, R₃₄ represents hydroxyl group, C₆₋₂₀ aromatichydrocarbon group which may be substituted by an alkoxy group, or CO₂R₃₅group, and R₃₅ represents C₁₋₂₀ hydrocarbon group, preferably an acidunstable group.

In the case described above, examples of the C₁₋₂₀ linear, branched, orcyclic alkyl group include methyl group, ethyl group, propyl group,isopropyl group, n-butyl group, sec-butyl group, tert-butyl group,cyclopentyl group, cyclohexyl group, 2-ethylhexyl group, n-octyl group,etc., and use of one having the number of carbon atoms of 1-12,particularly one having the number of carbon atoms of 1-10, ispreferable. Note that the fluorinated alkyl group means that a part orall of hydrogen atoms in the above-mentioned alkyl group are substitutedwith fluorine atoms, and examples thereof include trifluoromethyl group,2,2,2-trifluoroethyl group, 3,3,3-trifluoropropyl group, and1,1,2,3,3,3-hexafluoropropyl group.

R₃₄ represents hydroxyl group or C₆₋₂₀ aromatic hydrocarbon group whosehydrogen atoms may be substituted by a substituted hydroxyl group, andspecific examples thereof include a substituent group which may beexpressed by the following formula (IV):

wherein R₄₀ represents linear, branched, or cyclic alkyl group orfluorinated alkyl group, and specific examples thereof include the samesubstituents described for the above R₃₁, X represents fluorine atom,R₄₁ represents C₁₋₂₀ hydrocarbon group, preferably an acid unstablegroup. Also, each of a, b, c, and d represents 0 or an integer of 1-5,and a+b+c+d is any one of 0-5.

In R₄₁, examples of C₁₋₂₀ hydrocarbon group include the samesubstituents described for R₁. Also, although the acid unstable groupmay be selected from various groups, specific examples thereof includegroups represented by the following formula (V), (VI), or (VII),trialkylsilyl group in which the number of carbon atoms in each alkylgroup is 1-6, C₄₋₂₀ oxoalkyl group and so forth:

wherein R₅₁, and R₅₄ in the formulae (V) and (VI), respectively,represents monovalent hydrocarbon group, such as C₁₋₂₀ linear, branched,and cyclic alkyl group, which may include a hetero atom, such as oxygenatom, sulfur atom, nitrogen atom, and fluorine atom.

R₅₂ and R₅₃ represents hydrogen atom or C₁₋₂₀ linear, branched, orcyclic alkyl group, which may include a hetero atom, such as oxygenatom, sulfur atom, nitrogen atom, and fluorine atom. Also, R₅₂ and R₅₃,R₅₂ and R₅₄, and R₅₃ and R₅₄ may be bonded to each other to form a ring.Moreover, h represents 0 or an integer of 1-10.

More preferably, R₅₁ to R₅₄ are the following groups. R₅₁ is C₄₋₂₀, morepreferably C₄₋₁₅, tertiary alkyl group, in which each alkyl grouprepresents C₁₋₆ trialkylsilyl group, C₄₋₂₀ oxoalkyl group, or the groupexpressed by the above formula (VII). Specific examples of the tertiaryalkyl group include tert-butyl group, tert-amyl group, 1,1-diethylpropylgroup, 1-ethylcyclopentyl group, 1-butylcyclopentyl group,1-ethylcyclohexyl group, 1-butylcyclohexyl group,1-ethyl-2-cyclopentenyl group, 1-ethyl-2-cyclohexenyl group,2-methyl-2-adamantyl group and so forth. Specific examples of thetrialkylsilyl group include trimethylsilyl group, triethylsilyl group,dimethyl-tert-butylsilyl group and so forth. Specific examples of theoxoalkyl group include 3-oxocyclohexyl group, 4-methyl-2-oxooxane-4-ylgroup, 5-methyl-5-oxooxolane-4-yl, and so forth.

R₅₂ and R₅₃ represent hydrogen atom or C₁₋₁₈, more preferably C₁₋₁₀,linear, branched, or cyclic alkyl group, and specific examples thereofinclude methyl group, ethyl group, propyl group, isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, cyclopentyl group,cyclohexyl group, 2-ethylhexyl group, n-octyl group and so forth. Also,R₅₄ represents C₁₋₁₈, more preferably C₁₋₁₀, monovalent hydrocarbongroup which may have a hetero atom, such as oxygen, and includes linear,branched, or cyclic alkyl group, and those in which a part of hydrogenatoms thereof is substituted with hydroxyl group, alkoxy group, oxogroup, amino group, alkylamino group. Specific examples thereof includesubstituted alkyl group, such as 4-hydroxybutyl group, 2-butoxyethylgroup, 4-hydroxymethyl-1-cyclohexylmethyl group, 2-hydroxyethoxy-2-ethylgroup, 6-hydroxyhexyl group, and 1,3-dioxolane-2-one-4-methyl group.

Also, R₅₂ and R₅₃, R₅₂ and R₅₄, and R₅₃ and R₅₄ may form a ring, andwhen such a ring is formed, each of R₅₂, R₅₃, and R₅₄ represents C₁₋₁₈,more preferably C₁₋₁₀, linear or branched alkylene group.

Specific examples of the group expressed by the above formula (V)include t-butoxycarbonyl group, t-butoxycarbonylmethyl group,t-amyloxycarbonyl group, t-amyloxycarbonylmethyl group,1,1-diethylpropyloxycarbonyl group, 1,1-diethylpropyloxycarbonylmethylgroup, 1-ethylcyclopentyloxycarbonyl group,1-ethycyclopentyloxycarbonylmethyl group,1-ethyl-2-cyclopentenyloxycarbonyl group,1-ethyl-2-cyclopentenyloxycarbonylmethyl group,1-ethoxyethoxycarbonylmethyl group, 2-tetrahydropyranyloxycarbonylmethylgroup, and 2-tetrahydrofuranyloxycarbonylmethyl group.

Specific examples of linear or branched acid unstable group expressed bythe above formula (VI) include methoxymethyl group, ethoxymethyl group,n-propoxymethyl group, n-butoxymethyl group, isopropoxymethyl group,t-butoxymethyl group, 1-methoxy-ethyl group, 1-ethoxy-ethyl group,1-methoxy-propyl group, 1-methoxy-butyl group, 1-ethoxy-propyl group,1-ethoxy-propyl group, 1-ethoxy-propyl group, 1-n-propoxyethyl group,1-n-propoxyethyl group, 1-n-propoxyethyl group, 1-n-propoxy-propylgroup, 1-n-butoxy-butyl group, 1-n-propoxy-butyl group,1-cyclopentyloxy-ethyl group, 1-cyclohexyloxy-ethyl group,2-methoxy-2-propyl group, 2-ethoxy-2-propyl group, and so forth.

Specific examples of the acid unstable group expressed by the aboveformula (VI) which form a ring shape include tetrahydrofuran-2-yl group,2-methyltetrahydrofuran-2-yl group, tetrahydropyran-2-yl group,2-methyltetrahydropyran-2-yl group and so forth. As the formula (4),1-ethoxy-ethyl group, 1-n-butoxy-ethyl group, and 1-ethoxy-n-propylgroup are preferable.

In the formula (VII), R₅₅, R₅₆, and R₅₇ represent monovalent hydrocarbongroup, such as C₁₋₂₀ linear, branched, or cyclic alkyl group, which mayhave a hetero atom, such as oxygen atom, sulfur atom, and nitrogen atom,and fluorine atom. Also, R₅₅ and R₅₆, R₅₅ and R₅₇, and R₅₆ and R₅₇ maybe bonded to each other to form a ring.

Examples of the tertiary alkyl group which is expressed by the formula(VII) include t-butyl group, 1,1-diethyl-n-propyl group,1-ethylnorbonryl group, 1-methylcyclohexyl group, 1-ethylcyclopentylgroup, 2-(2-methyl)adamantyl group, 2-(2-ethyl)adamantyl group,tert-amyl group and so forth.

Also, specific examples of the tertiary alkyl group which is expressedby the formula (VII) may include the following functional groups:

wherein R₆₁ and R₆₄ represent C₁₋₆ linear, branched, or cyclic alkylgroup, and specific examples thereof include methyl group, ethyl group,propyl group, isopropyl group, n-butyl group, sec-butyl group, n-pentylgroup, n-hexyl group, cyclopropyl group, cyclopropylmethyl group, and soforth. Also, R₆₂ represents hydrogen atom, C₁₋₆ monovalent hydrocarbongroup which may include hetero atom, or monovalent hydrocarbon atom,such as C₁₋₆ alkyl group which may contain hetero atoms therein.Examples of the hetero atom include oxygen atom, sulfur atom, andnitrogen atom, and these atoms may be included or inserted in the formof —OH, —OR (wherein R represents C₁₋₂₀, particularly C₁₋₁₆, alkylgroup, the same definition will be applied hereinafter), —O—, —S—,—S(═O)—, —NH₂, —NHR, —NR₂, —NH—, and —NR—.

Also, R₆₃ represents hydrogen atom, C₁₋₂₀, particularly C₁₋₁₆ alkylgroup, hydroxyalkyl group, alkoxyalkyl group, alkoxy group, alkoxyalkylgroup, and so forth, and these may be linear, branched or cyclic.Specific examples thereof include methyl group, hydroxymethyl group,ethyl group, hydroxyethyl group, propyl group, isopropyl group, n-butylgroup, sec-butyl group, n-pentyl group, n-hexyl group, methoxy group,methoxymethoxy group, ethoxy group, tert-butoxy group, and so forth.

Moreover, examples of the trialkylsilyl group in which the number ofcarbon atoms in each alkyl group is 1-6 that may be used as an acidunstable group of R₄₁ include trimethylsilyl group, triethylsilyl group,tert-butyldimethylsilyl group, and so forth.

Furthermore, examples of C₄₋₂₀ oxoalkyl group which may be used as anacid unstable group of R₄₁ include 3-oxocyclohexyl group and the groupsexpressed by the following formulae:

Also, the above acid unstable group of R₄₁ may be an acetal cross-linkedgroup expressed by the following formula (VIII) or (IX):

wherein R₇₁ and R₇₂ represents hydrogen atom or C₁₋₈ linear, branched,or cyclic alkyl group, or R₇₁ and R₇₂ may be bonded to each other toform a ring. When a ring is formed, R₇₁ and R₇₂ represent linear orbranched alkylene group having the number of carbon atoms of 1-8. R₇₃represents linear, branched, or cyclic alkylene group having the numberof carbon atoms of 1-10. Also, e represents an integer of 1-7, and f andg represents 0 or an integer of 1-10. A represents C₁₋₅₀ aliphatic groupor saturated alicyclic hydrocarbon group having valency of (e+1),aromatic hydrocarbon group, or hetero cyclic group, and these groups mayinclude intervened hetero atoms, or a part of hydrogen atoms which arebonded to carbon atoms thereof may be substituted with hydroxyl group,carboxyl group, carbonyl group, or fluorine atom. B represents —CO—O—,—NHCO—O—, or —NHCONH—.

Specific examples of the cross-linked acetal expressed by the formulae(VIII) and (IX) include the following:

Specific examples of the repeating unit (III) having the functionalgroup expressed by the formula (IV) include repeating units which may beobtained by polymerizing the following monomers:

Styrene, α-methylstyrene, chlorostyrene, 1,1-diphenylethylene, stilbene,4-hydroxystyrene, 4-hydroxy-α-methylstyrene, 4-hydroxy-3-methyl-styrene,4-t-butoxy-styrene, 4-tetrahydropyranyloxy-styrene,4-phenoxyethoxy-styrene, 4-trimethylsilyloxy-styrene,4-t-butoxycarbonyloxy-styrene, 4-t-butoxycarbonylmethoxy-styrene,2,3-difluoro-4-hydroxystyrene, 2,3-difluoro-4-t-butoxy-styrene,2,6-difluoro-4-hydroxy-styrene, 2,6-difluoro-4-t-butoxy-styrene,3,5-difluoro-4-hydroxy-styrene, 3,5-difluoro-4-t-butoxy-styrene,2,3,5,6-tetrafluoro-4-hydroxy-styrene,2,3,5,6-tetrafluoro-4-t-butoxy-styrene,2-trifluoromethyl-4-hydroxy-styrene,2-trifluoromethyl-4-t-butoxy-styrene,2-trifluoromethyl-6-fluoro-4-hydroxy-styrene,2-trifluoromethyl-6-fluoro-4-t-butoxy-styrene,3-trifluoromethyl-5-fluoro-4-hydroxy-styrene,3-trifluoromethyl-5-fluoro-4-t-butoxy-styrene,4-(1-ethoxyethoxy)-styrene,4-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)-styrene,4-(2-ethoxymethoxy-1,1,1,3,3,3-hexafluoro-2-propyl)-styrene,2,3-difluoro-4-hydroxy-styrene,2,3-difluoro-4-t-butoxy-α-fluoro-styrene,2,6-difluoro-4-hydroxy-α-fluoro-styrene,2,6-difluoro-4-t-butoxy-α-fluoro-styrene,3,5-difluoro-4-hydroxy-α-fluoro-styrene,3,5-difluoro-4-t-butoxy-α-fluoro-styrene,2,3,5,6-tetrafluoro-4-hydroxy-α-fluoro-styrene,2,3,5,6-tetrafluoro-4-t-butoxy-α-fluoro-styrene,2-trifluoromethyl-4-hydroxy-α-fluoro-styrene,2-trifluoromethyl-4-t-butoxy-α-fluoro-styrene,2-trifluoromethyl-6-fluoro-4-hydroxy-α-fluoro-styrene,2-trifluoromethyl-6-fluoro-4-t-butoxy-α-fluoro-styrene,3-trifluoromethyl-5-fluoro-4-hydroxy-α-fluoro-styrene,3-trifluoromethyl-5-fluoro-4-t-butoxy-α-fluoro-styrene,4-(1-ethoxyethoxy)-α-methyl-styrene,4-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)-α-fluoro-styrene,4-(2-ethoxymethoxy-1,1,1,3,3,3-hexafluoro-2-propyl)-α-fluoro-styrene,and so forth.

Also, when R₃₄ is CO₂R₃₅ group, examples of R₃₅ include the samesubstituent groups as those described for R₄. In such a case, ascombinations of R₃₁-R₃₃, those represented by the following formula maybe preferably used (these may be obtained when the following compoundsare polymerized and indicate a repeating unit).

Specific examples of the repeating units having CO₂R₃₅ group includerepeating units which may be derived from acrylates, such as methylacrylate, ethyl acrylate, propyl acrylate, amyl acrylate, cyclohexylacrylate, ethylhexyl acrylate, octyl acrylate, t-octyl acrylate,chlorethyl acrylate, 2-ethoxyethyl acrylate, 2,2-dimethyl-3-ethoxypropylacrylate, 5-ethoxypentyl acrylate, 1-methoxyethyl acrylate,1-ethoxyethyl acrylate, 1-methoxypropyl acrylate,1-methyl-1-methoxyethyl acrylate, 1-(isopropoxy)ethyl acrylate, benzylacrylate, methoxybenzyl acrylate, furfuryl acrylate, andtetrahydrofurfuryl acrylate, methacrylates, such as methyl methacrylate,ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, amylmethacrylate, hexyl methacrylate, cyclohexyl methacrylate, benzylmethacrylate, chlorbenzyl methacrylate, octyl methacrylate,2-ethoxyethyl methacrylate, 4-methoxybutyl methacrylate, 5-methoxypentylmethacrylate, 2,2-dimethyl-3-ethoxypropyl methacrylate, 1-methoxyethylmethacrylate, 1-ethoxyethyl methacrylate, 1-methoxypropyl methacrylate,1-methyl-1-methoxyethyl methacrylate, 1-(isopropoxy)ethyl methacrylate,furfuryl methacrylate, and tetrahydrofurfuryl methacrylate, crotonates,such as methyl crotonate, ethyl crotonate, propyl crotonate, amylcrotonate, cyclohexyl crotonate, ethylhexyl crotonate, octyl crotonate,t-octyl crotonate, chloroethyl crotonate, 2-ethoxyethyl crotonate,2,2-dimethyl-3-ethoxypropyl crotonate, 5-ethoxypentyl crotonate,1-methoxyethyl crotonate, 1-ethoxyethyl crotonate, 1-methoxypropylcrotonate, 1-methyl-1-methoxyethyl crotonate, 1-(isopropoxy)ethylcrotonate, benzyl crotonate, methoxybenzyl crotonate, furfurylcrotonate, and tetrahydrofurfuryl crotonate, itaconates, such asdimethyl itaconate, diethyl itaconate, dipropyl itaconate, diamylitaconate, dicyclohexyl itaconate, bis(ethylhexyl) itaconate, dioctylitaconate, di-t-octyl itaconate, bis(chloroethyl) itaconate,bis(2-ethoxyethyl) itaconate, bis(2,2-dimethyl-3-ethoxypropyl)itaconate, bis(5-ethoxypentyl) itaconate, bis(1-methoxyethyl) itaconate,bis(1-ethoxyethyl) itaconate, bis(1-methoxypropyl) itaconate,bis(1-methyl-1-methoxyethyl) itaconate, bis(1-(isopropoxy)ethyl)itaconate, dibenzyl itaconate, bis(methoxybenzyl) itaconate, difurfurylitaconate, ditetrahydrofurfuryl itaconate. Also, repeating unitsexpressed by the following formula may be included as the examplesthereof.

Also, examples of the repeating units other than those expressed by theformula (I) include compounds expressed by the formula (X):

wherein R₈₁ and R₈₂ independently represent hydrogen, halogen atom,C₁₋₂₀ hydrocarbon group, a heterocyclic group, a cyano group, a nitrogroup, C(═O)R₄ group, S(O)_(n)R₄ group, P(═O)(R₄)₂ group or M(R₄)₃group, and specific examples thereof include the same substituents asthose described for R₁.

As described above, the polymer having the repeating unit expressed bythe formula (I) of the present invention means polymers which includeonly the repeating unit expressed by the formula (I) and polymers whichinclude the repeating unit expressed by the formula (I) and repeatingunits expressed by other than the formula (I). The polymerized structureof the repeating unit expressed by the formula (I) with the repeatingunit other than the formula (I) is not particularly limited, and may bein any structure of random polymerization, block polymerization, partblock polymerization, and alternating polymerization.

Also, the mixing ratio of the repeating unit expressed by the formula(I) with the other repeating unit is not particularly limited, and maybe arbitrarily set within the range of 99/1 to 1/99 in molar ratio.

Although the number average molecular weight of the polymer includingthe repeating unit expressed by the formula (I) is not particularlylimited, it is preferably in the range of 2,000 to 50,000 inconsideration of dry etch resistance, alkali solubility, etc., when usedfor resists and so forth. Also, although the molecular weightdistribution, which is the ratio of the weight average molecular weight(Mw) with the number average molecular weight (Mn), is also notparticularly limited, it is preferably within the range of 1.01-3.00,more preferably within the range of 1.01-1.50 from the viewpoint ofcarrying out fine processes for resists and so forth.

Specific examples of methods for preparing polymers having the repeatingunit expressed by the formula (I) include a method in which keteneexpressed by the following formula (XI) and aldehyde expressed by thefollowing formula (XII) are anionically polymerized in the presence ofan anionic polymerization initiator:

wherein R₉₁, R₉₂, and R₉₃ correspond to R₁, R₂, and R₃, respectively,and exclude substituents which interfere with the anionicpolymerization, for example, a substituent having an active hydrogenatom, substituents which show reactivity with the anionic polymerizationinitiator, and so forth.

Solvent used for anionic polymerization are not particularly limited aslong as it does not involve the polymerization reaction and is a polarsolvent compatible with the polymer. Specific examples thereof includealiphatic hydrocarbons, such as n-hexane and n-heptane, alicyclichydrocarbons, such as cyclohexane and cyclopentane, aromatichydrocarbons, such as benzene and toluene, ethers, such as diethylether, tetrahydrofuran (THF), and dioxane, and organic solvent which isgenerally used for anionic polymerization, such as anisole, andhexamethylphosphoramide. These may be used singularly or in mixture oftwo or more.

Examples of the anionic polymerization initiator include an alkali metaland an organic alkali metal. Examples of the alkali metal includelithium, sodium, potassium, cesium, sodium-potassium alloy, and soforth. As the organic alkali metal, alkylate, allylate, arylate, etc.,of the above alkali metals may be used, and specific examples thereofinclude ethyl lithium, n-butyl lithium, sec-butyl lithium, t-butyllithium, ethyl sodium, lithium biphenyl, lithium naphthalene, lithiumtriphenyl, sodium naphthalene, potassium naphthalene, α-methylstyrenesodiumdianion, 1,1-diphenylhexyl lithium, 1,1-diphenyl-3-methylpentyllithium, 1,1-diphenylmethyl potassium, 1,4-dilithio-2-butene,1,6-dilithiohexane, polystylyl lithium, cumyl potassium, and cumylcesium. These compounds may be used singularly or in a mixture of two ormore.

In general, an living anionic polymerization is carried out by addingthe compounds expressed by the formula (XI) and (XII) to an anionicpolymerization initiator. The series of reactions is carried out at atemperature of −100 to 0° C., preferably −70 to −20° C. in the presenceof an inert gas, such as argon and nitrogen, or in a vacuum of highdegree. The molar ratio of the ketene expressed by the formula (XI) withthe aldehyde expressed by the formula (XII) is not particularly limited;however, it is preferable to be within the range of 99/1 to 50/50. Also,as described above, the ketene expressed by the formula (XI) and thealdehyde expressed by the formula (XII), respectively, may be usedsingularly or in a mixture of two or more.

Also, among polymers in which R₃ is a substituent expressed by theformula (II), compounds in which R₅ is hydrogen atom may be obtained bycarrying out a polymerization reaction using a compound havingfunctional groups other than hydrogen atom, and deprotecting thefunctional groups. In such a reaction, it is possible to deprotect onlya part of the above functional groups by controlling the reaction. Forexample, the reaction in which a part or all of protecting groups ofphenolic hydroxyl groups which are unstable in acid, may generally becarried out at a temperature range of room temperature to 150° C. usingan acidic agent, such as hydrochloric acid, nitric acid, hydrochloricacid gas, hydrobromic acid, p-toluene sulfonic acid, trifluoroaceticacid, methanesulfonic acid, trifluoromethane sulfonic acid, and heavysulphate expressed by the general formula XHSO₄ (wherein X is an alkalimetal, such as Li, Na, and K), as a catalyst under the presence of asingle or a mixed solvent, other than those described for the abovepolymerization reaction, of alcohols, such as methanol and ethanol,ketones, such as acetone and methylethylketone, polyol derivatives, suchas methyl Cellosolve and ethyl Cellosolve, and water. Also, for the casein which a silyl group is used as a protecting group, fluoride anioncompounds, such as quaternary ammonium fluoride, may even used.

Although a catalytic amount is sufficient for the amount of acidic agentused, it is generally in the range of 0.1 to 3 equivalents, preferably0.1 to 1 equivalents with respect to the number of moles of alkoxy group(OR₅ group) which is obtained by calculating an average molecular weightof the entire polymer from the molar fraction and molecular weight ofeach unit, and by calculating the number of moles of each unit from thetotal weight of the polymer, the average molecular weight, and the molarfraction.

Also, it is possible to introduce another functional group to thehydroxyl group part which is obtained as described above. Although theabove process is explained using R₃ substituent as an example, it ispossible to carry out the process for substituents similar to OR₅ on R₁and R₂.

Since polymers having the repeating unit expressed by the formula (I)has properties in which the main chain thereof is readily cleaved by anacid as described later in Examples, it may function as anacid-degradable composition in a composition including an acid or acompound capable of generating an acid in response to an externalstimulation, and may be suitably used as a resist composition inparticular. When it is used as a resist composition, it is possible tomix polymer therewith, which is conventionally used for a chemicalamplifier positive resist.

The acid used in the present invention is not particularly limited aslong as it is an acidic compound, and specific examples thereof includehydrochloric acid, nitric acid, phosphoric acid, phosphorus oxychloride,methane sulfonic acid, p-toluene sulfonic acid, p-toluene sulfonicacid.pyridinium salt, chlorsulfonic acid, trichloro acetic acid, benzoicacid, and so forth.

In a compound capable of generating acid in response to an externalstimulation, examples of the external stimulation include heat,pressure, radiation, and so forth, and a compound which generates acidby radiation (hereinafter referred to as “acid generator”) maypreferably be used when the above-mentioned composition is used as aresist composition in particular. The polymer having the repeating unitexpressed by the formula (I) and the acid generator are generally usedin a state being dissolved in solvent.

The acid generators used in the present invention are not particularlylimited as long as they are capable of generating acid by theirradiation of radiation and not affecting the formation of resistpatterns. In particular, acid generators which have excellent opticaltransparency in the vicinity of 248.4 nm so as to maintain hightransparency of a resist composition, or whose optical transparency isimproved by exposure to maintain the high transparency of a resistcomposition, or which exerts its effect even when added in a minuteamount due to its high acid generating efficiency are preferable.Specific examples of particularly preferable acid generators includecompounds expressed by the following formulae (XIII), (XVI), (XV),(XVI), and (XVII):

wherein R₁₀₀ and R₁₀₁ independently represent C₁₋₆ linear, branched, orcyclic alkyl or aralkyl group, and W represents sulfonyl group orcarbonyl group.

wherein R₁₀₃ and R₁₀₄ independently represents hydrogen atom, halogenatom, or C₁₋₄ alkyl group, and R₁₀₅ represents C₁₋₆ linear, branched orcyclic alkyl group, aralkyl group, or substituted or unsubstitutedphenyl group, and V represents sulfonyl group or carbonyl group.

wherein R₁₀₆, R₁₀₇ and R₁₀₈ independently represents hydrogen atom, C₁₋₆alkyl group, C₁₋₆ alkoxy group, or t-butoxycarbonyloxy group, R₁₀₉represents C₁₋₈ fluorinated alkyl group, substituted or unsubstitutedphenyl group, or 10-camphor group, Y represents sulfur atom or iodineatom, and z represents 0 when Y is iodine atom and z represents 1 when Yis sulfur atom.

wherein R₁₁₀ represents C₁₋₆ alkyl group, C₁₋₈ alkyl group includingfluorine, substituted or unsubstituted phenyl group, or 10-camphorgroup.

wherein R₁₁₁ and R₁₁₂ independently represents hydrogen atom, methylgroup, or ethyl group, or R₁₁₁ and R₁₁₂ may form aromatic ring group orbridged alicyclic hydrocarbon group having unsaturated bonding, R₁₁₃represents C₁₋₆ alkyl group, C₁₋₈ alkyl group including fluorine,substituted or unsubstituted phenyl group, or 10-camphor group.

Specific examples of the preferable acid generator which may beexpressed by the formula (XIII) include1-cyclohexylsulfonyl-1-(1,1-dimethylethylsulfonyl) diazomethane,bis(1,1-dimethylethylsulfonyl) diazomethane, bis(1-methylethylsulfonyl)diazomethane, bis(cyclohexylsulfonyl) diazomethane,1-cyclohexylsulfonyl-1-cyclohexylcarbonyl diazomethane,1-diazo-1-cyclohexylsulfonyl-3,3-dimethylbutan-2-one,1-diazo-1-(1,1-dimethylethylsulfonyl)-3,3-dimethylbutan-2-one, and soforth.

Specific examples of the acid generators expressed by the formula (XIV)include bis(p-toluenesulfonyl) diazomethane,bis(2,4-dimethylbenzenesulfonyl) diazomethane,bis(p-tert-butylphenylsulfonyl) diazomethane,bis(p-chlorbenzenesulfonyl) diazomethane,methylsulfonyl-p-toluenesulfonyl diazomethane,cyclohexylsulfonyl-p-toluenesulfonyl diazomethane,1-p-toluenesulfonyl-1-cyclohexylcarbonyl diazomethane,1-diazo-1-(p-toluenesulfonyl)-3,3-dimethylbutan-2-one, and so forth.

Specific examples of the acid generators expressed by the formula (XV)include triphenylsulfonium.trifluoromethane sulfonate,triphenylsulfonium.perfluorobutane sulfonate,triphenylsulfonium.perfluorooctane sulfonate,triphenylsulfonium.p-toluenesulfonate, triphenylsulfonium.10-camphorsulfonate, diphenyl-p-tolylsulfonium-trifluoromethane sulfonate,diphenyl-p-tolylsulfonium.perfluorobutane sulfonate,diphenyl-p-tolylsulfonium.perfluorooctane sulfonate,diphenyl-p-tolylsulfonium.p-toluenesulfonate,diphenyl-p-tolylsulfonium-10-camphor sulfonate,diphenyl-p-tert-butylphenylsulfonium.trifluoromethane sulfonate,diphenyl-p-tert-butylphenylsulfonium.perfluorobutane sulfonate,diphenyl-p-tert-butylphenylsulfonium.perfluorooctane sulfonate,diphenyl-p-tert-butylphenylsulfonium.p-toluenesulfonate,diphenyl-p-tert-butylphenylsulfonium.10-camphor sulfonate,diphenyl-p-tert-butylphenylsulfonium.p-fluorobenzenesulfonate,diphenyl-p-cyclohexylphenylsulfonium.trifluoromethane sulfonate,diphenyl-p-cyclohexylphenylsulfonium.perfluorobutane sulfonate,diphenyl-p-cyclohexylphenylsulfonium.perfluorooctane sulfonate,diphenyl-p-cyclohexylphenylsulfonium.p-toluene sulfonate,diphenyl-p-tert-butoxyphenylsulfonium trifluoromethane sulfonate,diphenyl-p-tert-butoxyphenylsulfonium.perfluorobutane sulfonate,diphenyl-p-tert-butoxyphenylsulfonium.perfluorooctane sulfonate,diphenyl-p-tert-butoxyphenylsulfonium.p-toluenesulfonate,diphenyl-p-tert-butoxycarbonyloxyphenylsulfonium.perfluorooctanesulfonate, diphenyl-p-tert-butoxycarbonyloxyphenylsulfonium-10-camphorsulfonate, diphenyl-p-tert-butoxycarbonyloxyphenylsulfonium.p-toluenesulfonate, 4,4′-di-tert-butyldiphenyliodonium-10-camphor sulfonate, andso forth.

Specific examples of the acid generators expressed by the formula (XVI)include 1,2,3-tris-methanesulfonyloxy benzene,1,2,3-tris-trifluoromethane sulfonyloxy benzene,1,2,3-tris-perfluorooctane sulfonyloxy benzene,1,2,3-tris-perfluorobutane sulfonyloxy benzene,1,2,3-tris-p-toluenesulfonyloxy benzene, 1,2,3-tris-10-camphorsulfonyloxy benzene, 1,2,3-tris-trifluoroacetyloxy benzene,1,2,4-tris-methanesulfonyloxy benzene, 1,2,4-tris-trifluoromethanesulfonyloxy benzene, 1,2,4-tris-3-tris-perfluorooctane sulfonyloxybenzene, 1,2,4-tris-p-toluenesulfonyloxy benzene,1,2,4-tris-perfluorobutane sulfonyloxy benzene, and so forth.

Examples of the acid generators expressed by the formula (XVII) include,for example, succinimide.trifluoromethane sulfonate,succinimide.perfluorobutane sulfonate, succinimide.perfluorooctanesulfonate, succinimide.p-toluenesulfonate, succinimide.10-compharsulfonate, succinimide.methane sulfonate, succinimide ˜1-methylethanesulfonate, succinimide.benzene sulfonate,dimethylsuccinimide.trifluoromethane sulfonate,dimethylsuccinimide.perfluorooctane sulfonate,dimethylsuccinimide.p-toluenesulfonate,phthalimide.trifluoromethanesulfonate, phthalimide.perfluorobutanesulfonate, phthalimide.perfluorooctane sulfonate,phthalimide.p-toluenesulfonate, phthalimide.10-comphar sulfonate,phthalimide.methanesulfonate, phthalimide.benzenesulfonate,5-norbonene-2,3-dicarboxyimide.trifluoromethane sulfonate,5-norbonene-2,3 -dicarboxyimide.perfluorobutane sulfonate,5-norbonene-2,3-dicarboxyimide perfluorooctane sulfonate,5-norbonene-2,3-dicarboxyimide.p-toluenesulfonate,5-norbonene-2,3-dicarboxyimide.10-camphar sulfonate,5-norbonene-2,3-dicarboxyimide.methanesulfonate, and so forth.

When used as a resist composition, it is preferable to mix at least onekind of polymer having the repeating unit expressed by the formula (I)with a polymer used for a conventional amplifier positive type resist,if necessary, and to combine with one or arbitrary two or more kinds ofacid generators expressed by the formula (XIII) to (XVII). Examples ofpreferable combination of two or more kinds of acid generators includean acid generator expressed by the formula (XIII) which has excellentoptical transparency to maintain high transparency of a resistcomposition, low temperature dependency in heating process (PEB) afterexposure, and generates weak acid by the exposure, with an acidgenerator expressed by the formula (XIV), (XV), (XVI), or (XVII) whichhas high acid generating efficiency at a certain exposure amount orgenerate strong acid. Such combinations are preferable from theviewpoint of improving the shape of edge portions of a pattern andremoving scum. Among such combinations, it is particularly preferable tocombine an acid generator expressed by the formula (XIII) with an acidgenerator expressed by the formula (XIV) and/or (XV).

Also, as for the structural ratio of acid generators when two or morekinds thereof are used, 1-70 parts by weight, preferably 10-50 parts byweight, of an acid generator expressed by the formula (XIV), (XV), or(XVI) may be present with respect to 100 parts by weight of acidgenerator expressed by the formula (XIII).

Moreover, various triphenylsulfonium salt and diphenyliodonium salt (PF₆⁻, AsF₆ ⁻, BF₄ ⁻ and so forth are counter anions of onium salts thereof)and tris(trichloromethyl)-s-triazine/triethanolamine,tris(trichloromethyl)-s-triazine/acetamide and so forth which areconventionally used may be utilized singularly or in mixture of two ormore, or these may be mixed with a compound expressed by the aboveformulae of (XIII) to (XVII).

Basic compounds which may be used for a resist composition of thepresent invention are not particularly limited as long as they arecapable of adjusting sensitivity by addition. Non-limited examplesthereof include basic compounds which are normally used in this field,such as, polyvinyl pyridine, poly(vinylpyridine/methylmethacrylate),pyridine, piperidine, tribenzylamine, N-methyl-2-pyrroridone, monoalkylamines (examples of alkyl groups include C₁₋₁₂ linear, branched, orcyclic alkyl group, and 2-methylcyclohexylamine, 4-tert-cyclohexylamine,etc., are preferable), dialkyl amines (examples of alkyl groups includeC₁₋₁₂ linear, branched, or cyclic alkyl group, and dicyclohexylamine,di-n-octylamine, etc., are preferable), trialkyl amines (examples ofalkyl groups include C₁₋₁₂ linear, branched, or cyclic alkyl group, andtri-n-propylamine, tri-n-butylamine, tri-n-octylamine, tri-n-hexylamine,triethylamine, dicyclohexylmethylamine, dicyclohexylethylamine,N-methyl-di-n-octylamine, dimethyl-n-dodecyl amine,tris(2-ethylhexyl)amine, etc., are preferable), mono, di, trialkanolamines (triisopropanol amine, triethanol amine, etc., are preferable),tris[2-(2-methoxyethoxy)ethyl] amine, tetraalkylammonium hydroxide(examples of alkyl groups include C₁₋₁₂ linear, branched, or cyclicalkyl group, and tetramethylammonium hydroxide, tetraethylammoniumhydroxide, tetra-n-propylammonium hydroxide, tetra-n-butylammoniumhydroxide, etc., are preferable), and so forth. The above basiccompounds are generally used in mixture of two or more.

Solvent which may be used for a resist composition of the presentinvention is not particularly limited as long as it is capable ofdissolving polymer having a repeating unit expressed by the formula (I),or the polymer, acid generators, basic compounds, and additives, such asultraviolet absorbents, acidic compounds, and surfactants, which may beadded if necessary. In general, however, those having excellent filmforming property and which do not absorb in the vicinity of 220-300 nmare preferable. Specific examples of these include methyl Cellosolveacetate, ethyl Cellosolve acetate, propylene glycolmonomethyletheracetate, propylene glycol monoethylether acetate, methyl lactate, ethyllactate, 2-ethoxyethyl acetate, methyl pyruvate, ethyl pyruvate,3-methoxy methylpropionate, 3-methoxy ethylpropionate, 2-hydroxyethybutyrate, 3-hydroxy ethylbutate, N-methyl-2-pyrrolidone,N,N-dimethylformamide, N,N-dimethyl acetoamide, γ-butyrolactone,γ-propyolactone, cyclohexanone, methyl ethyl ketone, 2-heptanone,1,4-dioxane, diethylene glycol monomethyl ether, diethylene glycoldimethyl ether, ethylene glycol monoisopropyl ether, and so forth. Theabove solvents are generally used singularly or in combination of two ormore.

In the resist composition of the present invention, the mixing ratio ofthe polymer having the repeating unit expressed by the formula (I) withthe acid generator is 1 to 30 parts by weight, preferably 1 to 20 partsby weight, of the acid generator with respect to 100 parts by weight ofthe polymer. The amount of basic compound in the resist composition ofthe present invention is 0.5 to 20 parts by weight, preferably 1 to 10parts by weight, with respect to 1,000 parts by weight of the polymer.Also, although the amount of solvent in the resist composition of thepresent invention is not particularly limited as long as it does notinterfere with the application of obtained positive type resistcomposition on a substrate, it is generally 1 to 20 parts by weight,preferably 1.5 to 10 parts by weight, with respect to 1 part by weightof the polymer.

Although the resist composition of the present invention includes theabove-mentioned four components, i.e., the polymer having the repeatingunit expressed by the formula (I), the acid generator, the basiccompound, and the solvent, as it main constituents, ultraviolet rayabsorbents or acidic compounds may be used, if necessary, in order tosolve the problem of scum or improve the state of edges at interfacesbetween a substrate. Also, a surfactant may be used in order to improvethe film forming properties, prevent radial unevenness, and increasewettability.

Examples of the ultraviolet absorbents which may be used for the resistcomposition of the present invention, if necessary, include9-diazofuorenone and derivatives thereof, 1-diazo-2-tetralone,2-diazo-1-tetralone, 9-diazo-10-phenantlone,2,2′,4,4′-tetrakis(o-naphtoquinone diazido-4-sulfonyloxy) benzophenone,2,2′,4,4′-tetrahydroxy benzophenone,1,2,3-tris(o-naphthoquinonediazido-4-sulfonyloxy) propane,9-(2-methoxyethoxy) methylanthracene, 9-(2-ethoxyethoxy)methylanthracene, 9-(4-methoxybutoxy) methylanthracene,9-anthracenemethyl acetate, dihydroxyflavanone, quercetin, trihydroxyflavanone, tetrahydroxy flavanone, 4′,6-dihydroxy-2-naphto benzophenone,4,4′-dihydroxy benzophenone, 2,2′,4,4′-tetrahydroxybenzophenone, and soforth.

Examples of the acidic compounds which may be used for the resistcomposition of the present invention, if necessary, include organicacids, such as phthalic acid, succinic acid, malonic acid, benzoic acid,salicylic acid, m-hydroxy benzoic acid, p-hydroxy benzoic acid, o-acetylbenzoic acid, o-acetyl oxybenzoic acid, o-nitro benzoic acid,thiosalicylic acid, and thionicotinic acid, salicylaldehyde,salicylhydroxamic acid, succinicimide, phthalicimide, saccharin,ascorbic acid, and so forth.

Also, examples of the surfactants include nonionic surfactants, such aspolyethylene glycol stearate, polyethylene glycol dilaurate,polyethylene glycol, polypropylene glycol, polyoxyethylene stearylether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether,polyoxyethylene nonyl ether, and polyoxyethylene octylphenyl ether,other various commercially available nonionic surfactants, fluorinecontaining nonionic surfactants, fluorine containing cationicsurfactants, and fluorine containing anionic surfactants. Among theabove surfactants, fluorine containing nonionic surfactants, such asFLORADO (a product of Sumitomo 3M Ltd.), SURFLON (a product of AsahiGlass Co., Ltd.), UNIDINE (a product of Daikin Industries, Ltd), (aproduct of Dainippon Ink and Chemicals Incorporated), and EFTOP (aproduct of Tochem Products Co., Ltd.), which have excellent resist filmforming properties are particularly preferable.

Moreover, diethyl phthalate, dibutyl phthalate, dipropyl phthalate,etc., may be used, if necessary, as a plasticizer.

Amount of the above ultraviolet ray absorbents, acidic compounds,surfactants, or plasticizers, which may be used if necessary, in theresist composition of the present invention is, for example, 0.1 to 10parts by weight, preferably 0.1 to 5 parts by weight, with respect to100 parts by weight of the polymer, respectively.

Formation of a pattern using the resist composition of the presentinvention is carried out, for example, as follows. The resistcomposition of the present invention is applied with rotation onto, forexample, a semiconductor substrate, such as a silicon wafer, or asemiconductor substrate on which a radiation absorbing coating (anycoating formed by rotation application of organic type antireflectionagent, baking, CVD of inorganic antireflection agent, or sputtering) sothat the thickness thereof becomes about 0.3 to 2 μm, and this ispre-baked, for example, in an oven at a temperature of 70 to 150° C. for10 to 30 minutes, or on a hotplate at a temperature of 70 to 150° C. for1 to 2 minutes. Then, a mask for forming a target pattern is held on theabove-mentioned resist film, and after irradiating far ultraviolet raysof 300 nm or less so that the exposure value becomes about 1 to 100mJ/cm², it is baked (PEB) on a hotplate at a temperature of 70 to 150°C. for 1 to 2 minutes. Then, a developing process is carried out bymeans of a conventional method of dipping (Dip) method, puddle method,or spray method, using developer, such as 0.1 to 5% tetramethyl ammoniumhydroxide (TMAH) aqueous solution to form a target pattern on thesubstrate.

The developer used for the above-mentioned pattern formation method maybe selected, depending on the solubility of the resist composition, fromalkali solution having appropriate concentration which makes thedifference in solubility of exposed parts and unexposed parts large, andis generally selected within the range of 0.01 to 20%. Also, examples ofthe alkali solution used include organic amines, such as TMAH, choline,and triethanol amine, and aqueous solution including inorganic alkali,such as NaOH and KOH.

The resist composition of the present invention generates acid by theirradiation of not only far-ultraviolet rays and KrF excimer laser beambut also i-ray exposure, electron beam, and soft X-rays, and ischemically amplified. Accordingly, the resist composition of the presentinvention is a resist composition which is capable of forming a patternby the irradiation of low exposure far-ultraviolet rays, KrF excimerlaser beam, i-ray exposure, electron beam, and soft X-rays usingchemical amplifying effect.

Next, effect of the polymer of the present invention when it is used asa resist composition will be explained with examples. First, acid isgenerated due to photo reaction at a part which is exposed to farultraviolet rays, KrF excimer laser beam, and so forth.

When the exposed part is subjected to a heat treatment after theexposure process, the ester groups in the main chain are cleaved tobecome low molecular weight oligomer or monomer which is alkali soluble,and is dissolved in developer during a developing process.

On the other hand, functional groups of unexposed parts are notsubjected to chemical changes by acids since no acids are generated, andhence are hardly dissolved in an alkali developer. Accordingly, the rateof dissolution in an alkali developer between the exposed parts and theunexposed parts becomes significantly large when a pattern is formedusing the resist composition of the present invention, and henceresolution is improved and DOF is enlarged.

Since the effects of this characteristic increase as the thickness ofthe resist film decreases, this is extremely advantageous for making theresist membrane thinner, which will become necessary for the designrules hereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between exposure dose and thethickness of a film in Examples 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be explained in detail withreference to Examples. However, the scope of the present invention isnot limited to these Examples by any means.

Hereinafter, methods for purifying reagents and solvent used in Examplesof the present invention will be explained.

Solvents and raw materials used were purified in accordance withordinary procedure. Tetrahydrofuran (THF) was distilled from sodiumbenzophenon ketyl. Ketens were distilled under reduced pressure afterreacting acid chloride with triethylamine in THF at room temperature.Lithium chloride was heated and dried in a polymerization containerunder vacuum pressure. Aldehydes were distilled under reduced pressureafter adding CaH₂.

As for lithium n-butyl (n-BuLi), a commercially available n-BuLi hexanesolution (1.6 mol/l) was used without any modification.

SYNTHETIC EXAMPLE 1 (1) Synthesis of Ethyl Phenyl Ketene (EPK)

A THF solution of 2-phenyl butyryl chloride (55 g, 0.3 mol) was addeddropwise to a mixture of triethyl amine (91 g, 0.9 mol) in THF undernitrogen atmosphere. After one hour, precipitated triethyl aminehydrochloride was filtered. Filtrate was distilled under reducedpressure and EPK was obtained (60-70° C./4 mmHg). Amount obtained was 30g (yield was 70%).

(2) Copolymerization of EPK with 4-methoxy benzaldehyde (MBA)

After 1.9 g (45 millimole) of lithium chloride was heated and driedunder vacuum, 100 ml of THF was added under nitrogen atmosphere and themixture was cooled to −40° C. After 4.4 g (32 millimole) of MBA and 4.4g (30 millimole) of EPK were added, 0.93 ml (1.5 millimole) of thehexane solution of n-BuLi, and the reaction was continued for 30 minutesat −40° C. After the reaction was terminated by adding methanol, it wasadded to a large quantity of methanol to cause reprecipitation. Theprecipitate thus obtained was filtered and dried under reduced pressure,and 8.5 g of white powdery polymer (a) was obtained. The polymer (a) wasanalyzed using gel permeation chromatography (hereinafter abbreviated as“GPC”), and it was found that the polymer was a monodisperse polymerhaving Mn of 4,700 and Mw/Mn of 1.16.

SYNTHETIC EXAMPLE 2 (1) Synthesis of 4-(2′-ethoxyethoxy) benzaldehyde(EEBA)

After dissolving 24.4 g (0.2 mole) of 4-hydroxy benzaldehyde in 200 mlof ethyl acetate, 21.6 g (0.3 mole) of ethyl vinyl ether and 0.2 ml (2millimole) of hydrochloric acid were added, and the mixture was stirredovernight at room temperature. Then, after adding Na₂CO₃ aqueoussolution to neutralize, the mixture was separated and the upper layerwas washed with water until pH thereof reached 7. After adding MgSO₄ todry, the mixture was filtered, concentrated and dried, and distilledunder reduced pressure to obtain EEBA (100-105° C./0.4 mmHg). Amountobtained was 20 g (yield was 50%).

(2) Copolymerization of EPK with EEBA

The same procedure as described in Synthetic Example 1 (2) was repeatedexcept that EEBA was used instead of MPA, and white powdery polymer (b)was obtained. The polymer (b) was analyzed using GPC, and it was foundthat the polymer was a monodisperse polymer having Mn of 4,800 and Mw/Mnof 1.25.

SYNTHETIC EXAMPLE 3 (1) 4-(t-butoxycarbonyloxy) benzaldehyde (BOCBA)

After dissolving 24.4 g (0.2 mole) of 4-hydroxy benzaldehyde in 200 mlof THF, 52.4 g (0.24 mole) of di-t-butyldicarbonate and 15 mg (0.2millimole) of N,N-dimethylamino pyridine were added, and the mixture wasstirred overnight at room temperature. Then, after adding Na₂CO₃ aqueoussolution to neutralize, the mixture was separated and the upper layerwas washed with water until pH thereof reached 7. After adding MgSO₄ todry, the mixture was filtered, concentrated, and recrystalized frommethanol to obtain BOCBA. Amount obtained was 35 g (yield was 80%).

(2) Copolymerization of EPK with BOCBA

The same procedure as described in Synthetic Example 1 (2) was repeatedexcept that BOCBA was used instead of MBA, and white powdery polymer (c)was obtained. The polymer (c) was analyzed using GPC, and it was foundthat the polymer was a monodisperse polymer having Mn of 5,000 and Mw/Mnof 1.16.

SYNTHETIC EXAMPLE 4 Copolymerization of EPK with MBA and BOCBA

The same procedure as described in Synthetic Example 1 (2) was repeatedexcept that MBA/BOCBA (molar ratio of 3/1) was used instead of MBA, andwhite powdery polymer (d) was obtained. The polymer (d) was analyzedusing GPC, and it was found that the polymer was a monodisperse polymerhaving Mn of 4,800 and Mw/Mn of 1.15. Also, the copolymerizationproportion measured by NMR was MBA/BOCBA=3/1.

SYNTHETIC EXAMPLE 5

Polymer (e) including the repeating unit expressed by the followingformula was prepared in accordance with the method described inMacromolecular, 2002, 35, 6149:

SYNTHETIC EXAMPLE 6

After heating and vacuum drying 2.5 g (60 millimole) of lithiumchloride, 60 ml of THF was added under nitrogen atmosphere, and themixture was cooled to −40° C. Then, after adding 1.2 ml (2 millimole) ofthe hexane solution of n-BuLi, a mixed solution of 3.8 g (28 millimole)of MBA, 3.1 g (14 millimole) of BOCBA, 5.8 g (40 millimole) of EPK, and20 ml of THF was added dropwise, and the reaction was continued for 30minutes at −40° C. After the reaction was terminated by adding methanol,it was added to a large quantity of methanol to cause reprecipitation.The precipitates thus obtained was filtered and dried under reducedpressure, and 11 g of white powdery polymer 0) was obtained. The polymer0) was analyzed using GPC, and it was found that the polymer was amonodisperse polymer having Mn of 6,000 and Mw/Mn of 1.24. Also, thecopolymerization proportion measured by NMR was MBA/BOCBA=2/1.

SYNTHETIC EXAMPLE 7

After heating and vacuum drying 2.5 g (60 millimole) of lithiumchloride, 60 ml of THF was added under nitrogen atmosphere, and themixture was cooled to −40° C. Then, after adding 1.2 ml (2 millimole) ofthe hexane solution of n-BuLi, a mixed solution of 1.5 g (11 millimole)of MBA, 7.1 g (32 millimole) of BOCBA, 5.8 g (40 millimole) of EPK, and20 ml of THF was added dropwise, and the reaction was continued for 30minutes at −40° C. After the reaction was terminated by adding methanol,it was added to a large quantity of methanol to cause reprecipitation.The precipitate thus obtained was filtered and dried under reducedpressure, and 14 g of white powdery polymer (k) was obtained. Thepolymer (k) was analyzed using GPC, and it was found that the polymerwas a monodisperse polymer having Mn of 6,600 and Mw/Mn of 1.20. Also,the copolymerization proportion measured by NMR was MBA/BOCBA=1/3.

SYNTHETIC EXAMPLE 8

After heating and vacuum drying 2.5 g (60 millimole) of lithiumchloride, 60 ml of THF was added under nitrogen atmosphere, and themixture was cooled to −40° C. Then, after adding 1.2 ml (2 millimole) ofthe hexane solution of n-BuLi, a mixed solution of 9.3 g (42 millimole)of BOCBA, 5.8 g (40 millimole) of EPK, and 20 ml of THF was addeddropwise, and the reaction was continued for 30 minutes at −40° C. Afterthe reaction was terminated by adding methanol, it was added to a largequantity of methanol to cause reprecipitation. The precipitate thusobtained was filtered and dried under reduced pressure, and 13 g ofwhite powdery polymer (1) was obtained. The polymer (1) was analyzedusing GPC, and it was found that the polymer was a monodisperse polymerhaving Mn of 8,000 and Mw/Mn of 1.16.

REFERENCE EXAMPLE 1

After dissolving 50 g of poly(p-hydroxy styrene) (VP-8000, a product ofNippon Soda Co., Ltd., Mn=10,000, and Mw/Mn=1.13) in 200 ml of THF undernitrogen atmosphere, 60 mg of N,N-diamino pyridine and 11 g ofdi-t-butyl carbonate were added, and the mixture was stirred for one dayat room temperature. Then, after concentrating the reaction solution,the concentrated solution was added to a large quantity of methanol toprecipitate polymer, and polymer (f) was obtained after filtration,washing, and vacuum drying. The polymer (f) was analyzed using GPC, andit had Mn of 14,000 and Mw/Mn of 1.13.

REFERENCE EXAMPLE 2

After dissolving 50 g of poly(p-hydroxy styrene) (VP-8000, a product ofNippon Soda Co., Ltd., Mn=10,000, and Mw/Mn=1.13) in 200 ml of ethylacetate under nitrogen atmosphere, 58 g of ethyl vinyl ether and 0.3 mlof concentrated hydrochloric acid were added, and the mixture wasstirred for one day at room temperature. Then, after adding sodiumcarbonate to the reaction solution to separate, the solution was washedrepeatedly until it was neutralized. After being concentrated, thesolution was added to a large quantity of methanol to precipitatepolymer, and polymer (g) was obtained after filtration, washing, andvacuum drying. The polymer (g) was analyzed using GPC, and it had Mn of13,500 and Mw/Mn of 1.13.

REFERENCE EXAMPLE 3

After cooling 85 g of THF to −60° C. under nitrogen atmosphere, 7millimole of sec-butyl lithium was added and 14 g (0.1 mole) of t-butylmethacrylate was added dropwise. After the reaction was continued forone hour, the reaction was terminated by adding methanol, and it wasadded to a large quantity of methanol to precipitate polymer. Afterfiltration, washing, and vacuum drying, polymer (h) was obtained. Thepolymer (h) was analyzed using GPC, and it had Mn of 4,000 and Mw/Mn of1.10.

EXAMPLE 1

Each of the polymers (a) to (e) (5 g each) was dissolved in 50 ml oftoluene/ethanol mixed solvent, and after adding 150 mg of concentratedsulfuric acid, it was heated at 70° C. The rate of change in molecularweight was calculated using the following equation based on the changein molecular weight at an initial peak top and that at a peak top afterthe reaction using GPC:Rate of change in molecular weight=(initial molecular weight−molecularweight after reaction)/initial molecular weight×100Results are shown in Table 1

COMPARATIVE EXAMPLE 1

The reaction was carried out using the same condition as in Example 1except that polymers (f)-(h), and poly ε-caprolactone (a product of WakoPure Chemical Industries, Ltd., Mn=17,000, polymer (i)) were used. TABLE1 Reaction rate (%) Two-hour reaction Four-hour reaction Example 1Polymer (a) 5 10 Polymer (b) 60 70 Polymer (c) 60 70 Polymer (d) 20 25Polymer (e) 60 70 Comparative Polymer (f) 15 25 Example 2 Polymer (g) 2025 Polymer (h) 0 1 Polymer (i) 80 90

EXAMPLE 2

Each of the polymers (a) to (e) (100 mg each) was dissolved in 10 ml ofTHF, and after adding 3 mg of camphor sulfonic acid, it was cast toobtain a film of about 10 μm thickness. The obtained film was heated to140° C. The rate of change in molecular weight was calculated using thefollowing equation based on the change in molecular weight at an initialpeak top and that at a peak top after the reaction using GPC:Rate of change in molecular weight=(initial molecular weight−molecularweight after reaction)/initial molecular weight×100Results are shown in Table 2

COMPARATIVE EXAMPLE 2

The reaction was carried out using the same condition as in Example 2except that polymers (f)-(i) were used. Results are shown in Table 2.TABLE 2 Molecular weight rate of change (%) Two-minute Four-minutereaction reaction Example 1 Polymer (a) 5 15 Polymer (b) 95 95 Polymer(c) 95 95 Polymer (d) 30 35 Polymer (e) 95 95 Comparative Polymer (f) 2525 Example 2 Polymer (g) 20 25 Polymer (h) 0 5 Polymer (i) 3 5

EXAMPLE 3

A resist solution was prepared by dissolving polymers (j), (k), and (l)in propylene glycol monomethylether acetate (PGMEA) so that a resinsolid content concentration became 12%, and adding triphenyl sulfoniumtrifluoromethane sulfonate so that the content thereof became 1.0% byweight with respect to the resin solid content. A film of the aboveresist solution was formed on a silicon wafer using a spin coater (aproduct of Mikasa Co.), and it was heated at 90° C. on a hotplate for 60seconds to obtain a thin film of 400 nm thickness. After being exposedto light having a wavelength of 248 nm, it was heated at 110° C. on ahotplate for 90 seconds, and the film thickness thereof was measured.The relationship between the exposure dose and the film thickness isshown in FIG. 1.

As shown in FIG. 1, it was observed that the film thickness decreased byexposure and heating without being alkali developed. That is, main chainscission effectively occurred by the exposure, and the composition waschanged to low molecular compounds having high volatility.

EXAMPLE 4

A resist solution was prepared using the polymers (O) and (k) in thesame manner as in Example 3. A film was formed using the same method,and it was heated at 90° C. on a hotplate for 60 seconds to obtain athin film of 400 nm thickness. The obtained thin film was subjected toan RIE treatment using the following conditions, and the etching ratewas measured by measuring the film thickness. Results are tabulated inTable 3.

-   RIE Treatment Conditions-   Device: SAMCO load lock type RIE device MODEL RIE 200-L-   Gas: O₂: SF₆=5:30 (sccm)-   Pressure: 6 Pa-   Output: 150 W/24 cmΦ-   Time: 30 sec

COMPARATIVE EXAMPLE 3

The reaction was carried out as in Example 4 except that a commerciallyavailable resist material UV 82 (a product of Shipley Co.) was used.Results of the above are tabulated in Table 3. TABLE 3 Etching RelativeResist material rate (Å/sec) etching rate Example 4 Polymer (j) 42.930.92 Polymer (k) 46.43 0.99 C. Example 3 UV82 46.73 1.00

From the results shown in Table 3, it is clear that the compositions ofthe present invention have etching tolerance at least equal to that of acommercially available product.

Industrial Applicability

As described above, in the composition including ketene-aldehydecopolymer of the present invention, since main chains of the copolymerare cleaved by acid with high sensitivity so as to be decomposed to lowmolecular weight components, it becomes possible to significantly changethe properties of the composition before and after the decomposition.Also, the rate of acid decomposition, the molecular weight of decomposedproducts, etc., may be arbitrarily controlled based on thecopolymerization ratio of ketene and aldehyde, and the kind and ratio ofthe acid labile protecting group. Moreover, since it is possible tointroduce various substituents into side chains and the molecular weightthereof may be arbitrarily controlled, the acid degradable resincomposition of the present invention exhibits excellent effects as aresist material and has high industrial applicability.

1. An acid-degradable composition, comprising: a polymer having arepeating unit represented by the following general formula (I):

wherein R₁ and R₂ independently represent hydrogen atom, halogen atom,C₁₋₂₀ hydrocarbon group, a heterocyclic group, a cyano group, a nitrogroup, a C(═O)R₄ group, S(O)_(n)R₄ group, P(═O)(R₄)₂ group or M(R₄)₃group; R₃ represents C₁₋₂₀ hydrocarbon group or a heterocyclic group; R₄represents C₁₋₂₀ hydrocarbonoxy group, C₁₋₂₀ hydrocarbon group, C₁₋₂₀hydrocarbonthio group or mono- or di-C₁₋₂₀ hydrocarbonamino group; Mrepresents a silicon, germanium, tin or lead atom; and n is 0, 1 or 2;and an acid or a compound capable of generating an acid in response toan external stimulus.
 2. An acid-degradable composition according toclaim 1, wherein the external stimulus is at least one selected from thegroup consisting of heat, pressure, and radiation.
 3. An acid-degradablecomposition according to claim 1, wherein the compound capable ofgenerating an acid in response to an external stimulus is aphotosensitive compound which generates an acid by radiationirradiation.
 4. A photoresist composition, comprising: a polymercomponent having a repeating unit represented by the following generalformula (I):

wherein R₁ and R₂ independently represent hydrogen atom, halogen atom,C₁₋₂₀ hydrocarbon group, a heterocyclic group, a cyano group, a nitrogroup, a C(═O)R₄ group, S(O)_(n)R₄ group, P(═O)(R₄)₂ group or M(R₄)₃group; R₃ represents C₁₋₂₀ hydrocarbon group or a heterocyclic group: R₄represents C₁₋₂₀ hydrocarbonoxy group, C₁₋₂₀ hydrocarbon group, C₁₋₂₀hydrocarbonthio group or mono- or di- C₁₋₂₀ hydrocarbonamino group; andM represents a silicon, germanium, tin or lead atom.
 5. A photoresistcomposition, comprising the acid-degradable composition according toclaim
 1. 6. A photoresist composition according to claim 4, furthercomprising solvent.
 7. A photoresist composition according to claim 4,further comprising a basic compound.
 8. An acid-degradable compositionaccording to claim 1, wherein the R₁ and R₂ independently representC₁₋₂₀ hydrocarbon group, and the R₃ represents C₁₋₂₀ hydrocarbon groupor a heterocyclic group in the general formula (I).
 9. An aciddegradable-composition according to claim 1, wherein the R₃ in theformula (I) is a substituent represented by the following

formula (II): wherein R₅ represents hydrogen, or an aciddegradable.eliminable group, R₆ represents a halogen atom or C₁₋₂₀hydrocarbon group, m represents an integer of 1-3 and p represents 0 oran integer of 1-3 so as to satisfy m+p≦5, when p is 2 or greater, R₅ maybe the same or different from each other, and when p is 2 or greater, R₅may be the same or different from each other.
 10. An acid-degradablecomposition according to claim 1, wherein a number average molecularweight of the polymer having the repeating unit represented by theformula (I) is within a range of 2,000 to 50,000.
 11. An acid-degradablecomposition according to claim 1, wherein a ratio (Mw/Mn) of a weightaverage molecular weight (Mw) and a number average molecular weight (Mn)of the polymer having the repeating unit represented by the formula (I)is within a range of 1.01 to 3.00.
 12. A photoresist compositionaccording to claim 5, further comprising solvent.
 13. A photoresistcomposition according to claim 5, further comprising a basic compound.14. A photoresist composition according to claim 4, wherein the R₁ andR₂ independently represent C₁₋₂₀ hydrocarbon group, and the R₃represents C₁₋₂₀ hydrocarbon group or a heterocyclic group in thegeneral formula (I).
 15. A photoresist composition according to claim 4,wherein the R₃ in the formula (I) is a substituent represented by thefollowing formula (II): wherein R₅ represents hydrogen, or an aciddegradable.eliminable group, R₆ represents a halogen atom or C₁₋₂₀hydrocarbon group, m represents an integer of 1-3 and p represents 0 oran integer of 1-3 so as to satisfy m+p≦5, when p is 2 or greater, R₅ maybe the same or different from each other, and when p is 2 or greater, R₆may be the same or different from each other.
 16. A photoresistcomposition according to claim 4, wherein a number average molecularweight of the polymer having the repeating unit represented by theformula (I) is within a range of 2,000 to 50,000.
 17. A photoresistcomposition according to claim 4, wherein a ratio (Mw/Mn) of a weightaverage molecular weight (Mw) and a number average molecular weight (Mn)of the polymer having the repeating unit represented by the formula (I)is within a range of 1.01 to 3.00.